Paul Giamatti is surprise addition to Downton Abbey series 4 cast

Paul Giamatti is believed to be playing ‘playboy’ Harold Levinson (Picture: AP)

Emmy and Golden Globe-winning actor Paul Giamatti has joined the cast of Downton Abbey as Cora and Martha’s brother.

Giamatti, better known for his independent films and Shakespeare roles than prime-time TV period dramas, will play Harold Levinson, described as a ‘maverick playboy’.

The actor will feature in the Christmas episode, starring alongside Shirley MacLaine and the regular cast members in the climax to season four.

Carnival Films’ managing director, Gareth Neame said: ‘We’re excited that Paul Giamatti will be joining us on Downton to play Cora’s brother Harold, the rather free-spirited uncle to Mary and Edith. We can’t wait to see him work alongside Shirley Maclaine, who are both sure to upset the Grantham’s apple cart in this year’s Christmas Day episode.’

Paul Giamatti as Inspector Uhl in 2007 film The Illusionist (Picture: File)

Bolstering the show’s American contigent, Giamatti also joins Hugh Bonneville, Dame Maggie Smith, Michelle Dockery and Jim Carter on the cast, all of whom are expected to return for the series’ fourth run later in the year.

Giamatti is best known for his roles in films like American Splendor and Win Win, and next appears as Rhino in The Amazing Spider-Man 2.